After Brexit vote, what happens next in UK?

Britain's vote last week to leave the European Union has plunged the country into a triple crisis.

It has unleashed deep and bitter rifts within the main political parties, sent jolts of uncertainty through its economy and raised constitutional questions on the very future of United Kingdom.

Here are the main issues which the country has to grapple with:

- Lame-duck government -

David Cameron announced early Friday that he would resign, soon after the result came through. At that point he said he expected his successor as prime minister and Conservative leader to be in place by early October.

On Monday the Tories' committee in charge of the leadership election said the successor should be in place by September 2, "although an earlier conclusion may be possible," with nominations for the post formally closing on Thursday.

Frontrunners include former London mayor Boris Johnson, who spearheaded the Brexit campaign, and Home Secretary Theresa May.

After all those interested in the job have declared themselves, Conservative MPs will whittle the field down to two candidates.

The next prime minister is then decided by a postal vote of the Conservative party's membership of roughly 150,000 people.

- Warring opposition -

The leader of the main opposition Labour party, Jeremy Corbyn, has faced a revolt from his MPs over the referendum result. They accuse him of not having campaigned hard enough to prevent Brexit.

More than half of Corbyn's shadow cabinet had quit by Monday, when he was facing a no--confidence motion.

Despite the growing pressure, the veteran left-winger insists on staying put, claiming he has the support of the grassroots activists who propelled him to the leadership last year.

A Labour MP seeking to trigger a leadership challenge would need the support of 20 percent of their colleagues to get on the ballot. There would then be a ballot of party members.

- Defusing 'Remain' anger -

A small majority of voters backed leaving the EU on Thursday, but almost half voted to stay -- and many been venting their fury at the result ever since.

Over 3.6 million people and counting have signed a petition calling for a second referendum, while thousands of people are expected to join a march in London on Tuesday protesting at the result.

In Scotland, another region which voted overwhelmingly to remain in the EU, First Minister Nicola Sturgeon has indicated the result will trigger another referendum on independence.

She said another independence vote was justified even though separation was rejected in 2014 because the United Kingdom as it was then "does not exist any more".

Sturgeon said Scotland would seek direct talks with EU leaders and the Scottish parliament will be meeting on Tuesday to discuss the situation.

In Northern Ireland, which voted to remain, the Sinn Fein party has said the national result justified its call for a referendum on uniting with the Republic of Ireland.

- When to initiate exit talks -

Cameron insisted on Friday that he would not trigger Article 50 -- the formal process for starting a two-year process of negotiations to leave the EU -- instead leaving it to his successor.

But European leaders said this must happen as soon as possible, setting up a clash at a European summit in Brussels which Cameron will attend Tuesday.

Experts suggest that a delay in invoking Article 50 could be an attempt to help Britain secure more favourable terms of exit.

- Economic turbulence -

World stock markets have been volatile since the Brexit vote -- over two trillion dollars was wiped off market valuations on Friday, while shares in banks, airlines and property companies plunged again on Monday.

The pound has slumped to its lowest level in almost 31 years against the dollar and its lowest level in two years against the euro.

Some multinational companies have indicated they will pull jobs out of London in the wake of the vote.

Finance minister George Osborne sought to offer reassurance Monday about the future, insisting Britain was "ready to deal with the consequences".

The Bank of England is ready to provide £250 billion (300 billion euros, $330 billion) to support banks and markets while Business Secretary Sajid Javid will hold talks with business leaders this week.